&lt;title&gt;Fabrication and measured quality of the MMT primary mirror&lt;/title&gt;

Martin, Hubert M.; Allen, R. G.; Angel, J. R. P.; Burge, James H.; Davison, Warren B.; DeRigne, Scott T.; Dettmann, Lee R.; Ketelsen, Dean A.; Kittrell, W. C.; Miller, Stephen Matteo; Strittmatter, P. A.; West, Steve C.

doi:10.1117/12.319255

Cited by 13 publications

(4 citation statements)

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“…The optical finishing of the first 6.5 meter mirror is reported by Martin et al (1998a). This mirror is now being integrated into the telescope cell as reported by Martin et cii.…”

Section: Introductionmentioning

confidence: 83%

<title>Casting the first 8.4-m borosilicate honeycomb mirror for the Large Binocular Telescope</title>

et al. 1998

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We report on the casting of the first 8.4 meter diameter borosilicate honeycomb mirror at the Steward Observatory Mirror Laboratory. This blank will become the world's largest monolithic glass telescope mirror, and is the first of two mirrors for the Large Binocular Telescope Project. The honeycomb 8.4 meter mirror was cast from 21 tons of E6 borosilicate glass manufactured by Ohara. This glass is melted into a mold constructed of aluminosilicate fiber to produce a honeycomb structure with roughly 20% of solid density. The 1662 hexagonal voids that form the honeycomb structure are produced by ceramic fiber boxes bolted to the bottom of the mold with SiC bolts. The furnace rotates at 6.8 rpm during the casting process to produce the F/1.14 paraboloid on the front surface. This shaping minimizes the amount of glass which must be removed during the grinding process. The front faceplate of the mirror will be 28 mm thick after generating and the back faceplate will be 25 mm. The overall thickness of the finished honeycomb blank is 89 cm at the outer edge and 44 cm at the central hole. The first 8.4 meter mirror blank was cast in January 1997. During the casting, two tons of glass leaked from the mold inside the spinning furnace. After a three month annealing cycle the furnace was opened for inspection. As a result of the leakage about 2 square meters of the faceplate near one edge of the mirror was too thin to be polished. In April 1997, an additional two tons of glass was loaded on top of the intact honeycomb structure. In June 1997, after heating slowly back to the annealing temperature, this extra glass was flash melted onto the front of the blank to assure that the faceplate was of sufficient thickness. After a further three month annealing cycle, the furnace was re-opened to reveal a superb casting with low bubble content and little trace of the fusion boundary. The blank has been removed from the furnace using a fixture glued to the upper surface of the blank. It will soon be stripped of its mold material in preparation for polishing.

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“…The optical finishing of the first 6.5 meter mirror is reported by Martin et al (1998a). This mirror is now being integrated into the telescope cell as reported by Martin et cii.…”

Section: Introductionmentioning

confidence: 83%

<title>Casting the first 8.4-m borosilicate honeycomb mirror for the Large Binocular Telescope</title>

et al. 1998

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“…As a result, the 6.5m primary mirror fabrication project finished in 11 months using only two different sizes of tools. Overall it was three times more efficient than past 6.5m mirror fabrication projects [1], [2] performed at the University of Arizona, when considering actual processing time.…”

Section: Introductionmentioning

confidence: 91%

Process optimization for efficient convergence in large optics fabrication

Lowman

Martin

et al. 2018

Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation III

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Large optic fabrication is a delicate and time consuming process. Obtaining a large prime optic is often in the critical path of a project and poses a serious risk to both the schedule and budget. The Optical Engineering and Fabrication Facility (OEFF) at the College of Optical Sciences, the University of Arizona, has developed a new way of optimizing its large optic fabrication process for maximum efficiency in convergence. The new process optimization takes the amount of stock material removal, tool characteristics, metrology uncertainty, optic prescription, optic material properties, and resource availability as input parameters and provides an optimized process along with an achievable convergence. This paper presents technical details of the new process optimization and demonstrates performance on 6.5m mirror fabrication at the University of Arizona. Two case studies for an 8.4m GMT off-axis primary mirror segment and a 3.1m TMT convex secondary mirror fabrication are also presented.

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“…[16] The early 6.5-m primaries were polished and figured at the Mirror Lab. [17], [18] The most recent 6.5-m mirror was polished in the upgraded Optical Engineering and Fabrication Facility at the UA's College of Optical Sciences. Starting from the machined surface at 40 μm rms surface, the computer-controlled polishing system achieved an accuracy of 20 nm rms surface in only 39 calendar weeks.…”

Section: Optical Designsmentioning

confidence: 99%

An inexpensive turnkey 6.5-m observatory with customizing options

Kingsley

Angel

Davison

et al. 2018

Ground-Based and Airborne Telescopes VII

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A turnkey observatory with 6.5-m telescope has been developed for a broad range of science applications. The observatory includes the telescope, mount and enclosure, installed on site and ready for operation. The telescope's primary mirror is an f/1.25 honeycomb sandwich of Ohara E6 borosilicate glass, similar to that of the MMT and Magellan telescopes. The baseline optical design is for a Gregorian Nasmyth focus at f/11. A Gregorian adaptive optics secondary that provides a wide-field focus corrected for ground layer turbulence (0.25 arcsecond images over a 4 arcminute field) as well as a narrow-field diffraction-limited focus is optional. Another option is a corrected f/5 focus with a 1° field. The observatory, built by partners from academia and industry with extensive experience, can be delivered within five years at a fixed price.

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<title>Fabrication and measured quality of the MMT primary mirror</title>

Cited by 13 publications

References 1 publication

<title>Casting the first 8.4-m borosilicate honeycomb mirror for the Large Binocular Telescope</title>

<title>Casting the first 8.4-m borosilicate honeycomb mirror for the Large Binocular Telescope</title>

Process optimization for efficient convergence in large optics fabrication

An inexpensive turnkey 6.5-m observatory with customizing options

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